*Coefficient of Expansion : is
the average increase in length per unit
length per 0C change
in temperature over the range of 300C to 3000C.
Picture below further explains how this
expansion occurs with temperature variation.

*Density (D): is the weight (W) per unit volume (V) and the values listed are reported in grams per cubic centimeter.

*Softening Point: is the temperature at which a glass fiber of uniform diameter elongates at a specific rate under its own weight. In this temperature range glass will deform noticeably under its own weight. Softening point temperature corresponds to a viscosity of 107.6 poises.

*Working Point: is the temperature at which the glass has a viscosity of 104 poises. At this temperature the glass is sufficiently soft to be worked.

*Annealing Point: is the temperature at which the internal stresses caused by rapid cooling or forming temperature may be substantially removed in a matter of minutes.

*Chemical Durability: is the resistance of a glass to chemical attack by its environment. It is expressed by the amount of alkali released.